Although farmers routinely focus on protein, energy and phosphorus when balancing ruminant diets, the role of trace elements is often overlooked – sometimes with costly consequences. These micronutrients may be required in small quantities, but they underpin fertility, immunity, growth and overall herd performance. In this Q&A, Drs Willie Smith and Lourens Havenga explain why correct trace element supplementation is essential, how modern production systems have increased the risk of subclinical deficiencies, and what farmers should consider when choosing the right combination of licks and injections for their herds.
Question: How important is it to use trace elements and how should I administer them?
Answer: Essential trace elements are often the least acknowledged aspect of ruminant feeding because it is extremely difficult to diagnose deficiencies of these elements – especially when there are sub-optimal deficiencies and consequently no clinical signs are noticeable. Such deficiencies often result in significant economic loses. In a recent study it was shown that, 50 years ago, a single apple could satisfy a person’s daily iron requirements.
By 2006, that same person would have had to consume 26 apples in order to meet his daily iron requirements. The conclusion drawn in this study demonstrates the indisputable reality that repeated production on the same piece of land causes the trace element concentration in, for example, fruit, vegetables, grains and pastures to diminish progressively and that it is not replenished by fertilising.
Fertilisation programmes have, as their goal, achieving the best possible yield per hectare of land, without paying any attention to the trace element con tent of the harvest. Trace elements are carried off our farms in milk tankers (as milk) and in trucks carrying livestock (cattle and sheep that are to be sold or slaughtered) and are never replenished. It must be noted specifically that the attitude to, and the goals of, trace element supplementation in ruminants have changed dramatically over the past decade. The historical view of simply supplementing deficiencies has been replaced by a much more goal-orientated focus – to optimise the trace element status in advance of economically important events.
Stock farmers, vets, and animal husbandry experts have to ensure all livestock herds with which they are involved have specific, goal-orientated programmes for supplementing trace elements. Such programmes should not simply try to prevent trace element deficiencies. They should focus, in particular, on optimising the trace element status – especially the trace element functions of producing farm animals and breeding animals during economically critical events, such as calving and lambing, mating, rapid growth and adapting to stress.
Stock farmers often believe, erroneously, that fertility (efficient reproduction) is highly heritable and can quickly be improved by using the right bulls or rams, or the so-called fertile breeds. The heritability of fertility in cattle is less than 5%, and in sheep, between 8% and 20% (the more multiple births, the higher the heritability). The environment (feeding and management) thus plays a much greater role in fertility. The two most important nutrition-linked factors that will guarantee optimal fertility are body weight or condition at mating and trace element status. Selecting fertile, well-adapted animals on a specific farm should always be in terms of a long-term strategy, but remember that a good supplementation programme that will guarantee optimal condition and trace element status at lambing or calving is often worth more than that so-called “fertile” ram or bull.
Also read: Ask the vet | Trace elements for ruminants
Some important functions of the most important trace elements
- Zinc is essential for sexual maturity, the onset of oestrus and optimal fertility. Zinc is essential for complete testicular development, the quantity and quality of semen, as well as for libido.
- Manganese is essential for producing oestrogen, oestrus and ovulation as well as for normal testicular development. Manganese-deficient cows produce more bull calves than heifers.
- Marginal selenium levels lead to a compromised immune system, abortions, retained afterbirths and calves weak at birth.
- Optimal copper levels are essential for normal oestrus, conception, embryo survival and the viability of young calves. Along with phosphorus, copper is viewed as the most essential mineral for beef cattle production.
South Africa has world-class livestock experts (ruminant nutrition experts), and South African livestock farmers supplement their natural veld with macro-nutrients such as protein, energy and phosphorus, equally as well as, or better than, the best livestock farmers in the world.
Livestock experts and farmers should focus their attention more seriously on the trace element content of licks as well as efficient, goal-driven programmes for supplementing trace elements. A high intake of calcium and iron reduces the absorption of essential trace elements. Programmes for supplementing trace elements should not be based solely on licks because variations in the content of licks prevent, and bind, trace elements – particularly calcium, sulphur, molybdenum and/or iron – in the digestive tract, and so reduce their absorption significantly. This often leads to suboptimal trace element levels before calving or lambing, before mating, with vigorous young growth and with stress (adaptation).
In Southern Africa, drinking water (especially borehole water) for cattle often contains a lot of calcium and/or iron, which greatly impedes the absorption of essential trace elements. Programmes for supplementing trace elements in ruminants should always be based on two aspects; namely, oral supplementation (licks) and injections.
Injecting trace elements should take place four to six weeks before calving or lambing, and again four to six weeks before mating, to ensure that the functions of trace elements will be optimal when needed. Good-quality injectable trace element preparations, which contain the trace elements needed at the correct levels, have the advantage that the trace elements are not bound in the digestive tract and the animals can use them very efficiently.
When it comes to licks, the following should be noted:
Ensure that phosphate and protein licks, as well as those for energy or production, provide at least 50% of the total trace element requirement.
- Licks should contain zinc, manganese, selenium, copper, chrome, cobaltand iodine.
- Cattle have a greater need for copper than sheep. For this reason, generally speaking, cattle licks should contain more copper than sheep licks do. Assess the status of copper in the livers of your sheep before adding copper to licks. Consult your vet.
- Supplement iron only if it has been established conclusively that there is a deficiency. Basic feeds and drinking water usually contain more iron than ruminants need.
- Make sure that licks do not contain too much calcium, sulphur, iron, molybdenum or other elements known to impede the absorption of trace elements. Too much calcium and iron, in particular, are often provided, with detrimental results, because they bind the trace elements and so reduce their absorption.
- Always have licks containing trace elements available for animals, particularly from eight weeks before economically critical times. Note the following with regard to injectable trace element preparations:
- Use an injectable trace element preparation that has proven practical test results, as well as proven results for its bioavailability to provide what ruminants need before economically critical periods.
- Trace element injections for cattle should contain zinc, manganese, selenium, copper and chrome. Iodine should also be injected in areas where there is a real deficiency, such as the Pietermaritzburg region.
- Cobalt offers no benefit in an injectable product. It has to be taken by mouth, from where it goes to the rumen where microbes use it to produce vitamin B12 . If there is a cobalt deficiency, vitamin B12 may be injected.
- Animals should be injected four to six weeks before economically critical periods, and also when hormones are implanted.
Also read:
Supplement trace elements
Advice on using licks
